//    OpenVPN -- An application to securely tunnel IP networks
//               over a single port, with support for SSL/TLS-based
//               session authentication and key exchange,
//               packet encryption, packet authentication, and
//               packet compression.
//
//    Copyright (C) 2012-2022 OpenVPN Inc.
//
//    This program is free software: you can redistribute it and/or modify
//    it under the terms of the GNU Affero General Public License Version 3
//    as published by the Free Software Foundation.
//
//    This program is distributed in the hope that it will be useful,
//    but WITHOUT ANY WARRANTY; without even the implied warranty of
//    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
//    GNU Affero General Public License for more details.
//
//    You should have received a copy of the GNU Affero General Public License
//    along with this program in the COPYING file.
//    If not, see <http://www.gnu.org/licenses/>.

// TCP transport object specialized for client.

#ifndef OPENVPN_TRANSPORT_CLIENT_TCPCLI_H
#define OPENVPN_TRANSPORT_CLIENT_TCPCLI_H

#include <sstream>

#include <openvpn/io/io.hpp>

#include <openvpn/transport/tcplink.hpp>
#ifdef OPENVPN_TLS_LINK
#include <openvpn/transport/tlslink.hpp>
#endif
#include <openvpn/transport/client/transbase.hpp>
#include <openvpn/transport/socket_protect.hpp>
#include <openvpn/client/remotelist.hpp>

namespace openvpn {
namespace TCPTransport {

class ClientConfig : public TransportClientFactory
{
  public:
    typedef RCPtr<ClientConfig> Ptr;

    RemoteList::Ptr remote_list;
    size_t free_list_max_size;
    Frame::Ptr frame;
    SessionStats::Ptr stats;

    SocketProtect *socket_protect;

#ifdef OPENVPN_TLS_LINK
    bool use_tls = false;
    std::string tls_ca;
#endif

#ifdef OPENVPN_GREMLIN
    Gremlin::Config::Ptr gremlin_config;
#endif

    static Ptr new_obj()
    {
        return new ClientConfig;
    }

    TransportClient::Ptr new_transport_client_obj(openvpn_io::io_context &io_context,
                                                  TransportClientParent *parent) override;

    void process_push(const OptionList &opt) override
    {
        remote_list->process_push(opt);
    }

  private:
    ClientConfig()
        : free_list_max_size(8),
          socket_protect(nullptr)
    {
    }
};

class Client : public TransportClient, AsyncResolvableTCP
{
    typedef RCPtr<Client> Ptr;

    typedef TCPLink<openvpn_io::ip::tcp, Client *, false> LinkImpl;
#ifdef OPENVPN_TLS_LINK
    typedef TLSLink<openvpn_io::ip::tcp, Client *, false> LinkImplTLS;
#endif

    friend class ClientConfig; // calls constructor
    friend LinkImpl::Base;     // calls tcp_read_handler

  public:
    void transport_start() override
    {
        if (!impl)
        {
            halt = false;
            stop_requeueing = false;
            if (config->remote_list->endpoint_available(&server_host,
                                                        &server_port,
                                                        &server_protocol))
            {
                start_connect_();
            }
            else
            {
                parent->transport_pre_resolve();

                async_resolve_name(server_host, server_port);
            }
        }
    }

    bool transport_send_const(const Buffer &buf) override
    {
        return send_const(buf);
    }

    bool transport_send(BufferAllocated &buf) override
    {
        return send(buf);
    }

    bool transport_send_queue_empty() override
    {
        if (impl)
            return impl->send_queue_empty();
        else
            return false;
    }

    bool transport_has_send_queue() override
    {
        return true;
    }

    size_t transport_send_queue_size() override
    {
        if (impl)
            return impl->send_queue_size();
        else
            return 0;
    }

    void reset_align_adjust(const size_t align_adjust) override
    {
        if (impl)
            impl->reset_align_adjust(align_adjust);
    }

    void server_endpoint_info(std::string &host, std::string &port, std::string &proto, std::string &ip_addr) const override
    {
        host = server_host;
        port = server_port;
        const IP::Addr addr = server_endpoint_addr();
        proto = server_protocol.str();
        ip_addr = addr.to_string();
    }

    IP::Addr server_endpoint_addr() const override
    {
        return IP::Addr::from_asio(server_endpoint.address());
    }

    unsigned short server_endpoint_port() const override
    {
        return server_endpoint.port();
    }

    openvpn_io::detail::socket_type native_handle() override
    {
        return socket.native_handle();
    }

    Protocol transport_protocol() const override
    {
        return server_protocol;
    }

    void stop() override
    {
        stop_();
    }
    ~Client() override
    {
        stop_();
    }

  private:
    Client(openvpn_io::io_context &io_context_arg,
           ClientConfig *config_arg,
           TransportClientParent *parent_arg)
        : AsyncResolvableTCP(io_context_arg),
          io_context(io_context_arg),
          socket(io_context_arg),
          config(config_arg),
          parent(parent_arg),
          resolver(io_context_arg),
          halt(false),
          stop_requeueing(false)
    {
    }

    void transport_reparent(TransportClientParent *parent_arg) override
    {
        parent = parent_arg;
    }

    void transport_stop_requeueing() override
    {
        stop_requeueing = true;
    }

    bool send_const(const Buffer &cbuf)
    {
        if (impl)
        {
            BufferAllocated buf(cbuf, 0);
            return impl->send(buf);
        }
        else
            return false;
    }

    bool send(BufferAllocated &buf)
    {
        if (impl)
            return impl->send(buf);
        else
            return false;
    }

    void tcp_eof_handler() // called by LinkImpl::Base
    {
        config->stats->error(Error::NETWORK_EOF_ERROR);
        tcp_error_handler("NETWORK_EOF_ERROR");
    }

    bool tcp_read_handler(BufferAllocated &buf) // called by LinkImpl::Base
    {
        parent->transport_recv(buf);
        return !stop_requeueing;
    }

    void tcp_write_queue_needs_send() // called by LinkImpl::Base
    {
        parent->transport_needs_send();
    }

    void tcp_error_handler(const char *error) // called by LinkImpl::Base
    {
        std::ostringstream os;
        os << "Transport error on '" << server_host << ": " << error;
        stop();
        parent->transport_error(Error::TRANSPORT_ERROR, os.str());
    }

    void stop_()
    {
        if (!halt)
        {
            halt = true;
            if (impl)
                impl->stop();

            socket.close();
            resolver.cancel();
            async_resolve_cancel();
        }
    }

    // do DNS resolve
    void resolve_callback(const openvpn_io::error_code &error,
                          results_type results) override
    {
        if (!halt)
        {
            if (!error)
            {
                // save resolved endpoint list in remote_list
                config->remote_list->set_endpoint_range(results);
                start_connect_();
            }
            else
            {
                std::ostringstream os;
                os << "DNS resolve error on '" << server_host << "' for " << server_protocol.str() << " session: " << error.message();
                config->stats->error(Error::RESOLVE_ERROR);
                stop();
                parent->transport_error(Error::UNDEF, os.str());
            }
        }
    }

    // do TCP connect
    void start_connect_()
    {
        config->remote_list->get_endpoint(server_endpoint);
        OPENVPN_LOG("Contacting " << server_endpoint << " via "
                                  << server_protocol.str());
        parent->transport_wait();
        socket.open(server_endpoint.protocol());

        if (config->socket_protect)
        {
            if (!config->socket_protect->socket_protect(socket.native_handle(), server_endpoint_addr()))
            {
                config->stats->error(Error::SOCKET_PROTECT_ERROR);
                stop();
                parent->transport_error(Error::UNDEF, "socket_protect error (" + std::string(server_protocol.str()) + ")");
                return;
            }
        }

        socket.set_option(openvpn_io::ip::tcp::no_delay(true));
        socket.async_connect(server_endpoint, [self = Ptr(this)](const openvpn_io::error_code &error)
                             {
                                                OPENVPN_ASYNC_HANDLER;
                                                self->start_impl_(error); });
    }

    // start I/O on TCP socket
    void start_impl_(const openvpn_io::error_code &error)
    {
        if (!halt)
        {
            if (!error)
            {
#ifdef OPENVPN_TLS_LINK
                if (config->use_tls)
                {
                    int flags = SSLConst::LOG_VERIFY_STATUS | SSLConst::ENABLE_CLIENT_SNI;
                    SSLLib::SSLAPI::Config::Ptr ssl_conf;
                    ssl_conf.reset(new SSLLib::SSLAPI::Config());
                    ssl_conf->set_mode(Mode(Mode::CLIENT));
                    ssl_conf->set_local_cert_enabled(false);
                    ssl_conf->set_frame(config->frame);
                    ssl_conf->set_rng(new SSLLib::RandomAPI());

                    if (!config->tls_ca.empty())
                    {
                        ssl_conf->load_ca(config->tls_ca, true);
                    }
                    else
                    {
                        flags |= SSLConst::NO_VERIFY_PEER;
                    }

                    ssl_conf->set_flags(flags);
                    ssl_factory = ssl_conf->new_factory();

                    impl.reset(new LinkImplTLS(this,
                                               io_context,
                                               socket,
                                               0,
                                               config->free_list_max_size,
                                               config->frame,
                                               config->stats,
                                               ssl_factory));
                }
                else
#endif
                    impl.reset(new LinkImpl(this,
                                            socket,
                                            0, // send_queue_max_size is unlimited because we regulate size in cliproto.hpp
                                            config->free_list_max_size,
                                            (*config->frame)[Frame::READ_LINK_TCP],
                                            config->stats));

#ifdef OPENVPN_GREMLIN
                impl->gremlin_config(config->gremlin_config);
#endif
                impl->start();
                if (!parent->transport_is_openvpn_protocol())
                    impl->set_raw_mode(true);
                parent->transport_connecting();
            }
            else
            {
                std::ostringstream os;
                os << server_protocol.str() << " connect error on '" << server_host << ':' << server_port << "' (" << server_endpoint << "): " << error.message();
                config->stats->error(Error::TCP_CONNECT_ERROR);
                stop();
                parent->transport_error(Error::UNDEF, os.str());
            }
        }
    }

    std::string server_host;
    std::string server_port;
    Protocol server_protocol;

    openvpn_io::io_context &io_context;
    openvpn_io::ip::tcp::socket socket;
    ClientConfig::Ptr config;
    TransportClientParent *parent;
    LinkBase::Ptr impl;
    openvpn_io::ip::tcp::resolver resolver;
    LinkImpl::Base::protocol::endpoint server_endpoint;
    bool halt;
    bool stop_requeueing;

#ifdef OPENVPN_TLS_LINK
    SSLFactoryAPI::Ptr ssl_factory;
#endif
};

inline TransportClient::Ptr ClientConfig::new_transport_client_obj(openvpn_io::io_context &io_context,
                                                                   TransportClientParent *parent)
{
    return TransportClient::Ptr(new Client(io_context, this, parent));
}
} // namespace TCPTransport
} // namespace openvpn

#endif
